The present invention relates to a transmission for transmitting a torque from an input shaft to an output shaft.
JP-A-11-264449 discloses a transmission including coaxial input and output shafts, a bypass torque path for transmitting a torque from the input shaft to the output shaft through an intermediate shaft extending parallel to the coaxial input and output shafts and two gear trains, and a pair of input clutches one of which transmits the torque from the input shaft to the output shaft through selected one of gear pairs of respective shift stages, and another one of which transmits the torque from the input shaft to the output shaft without changing a rotational speed between the input and output shafts.
JP-A-61-45163 discloses a transmission in which a torque is transmitted from an input shaft to an output shaft during a shifting operation through the last shift stage (smallest reduction ratio shift stage) gear pair.
An object of the present invention is to provide a transmission in which an engage and/or disengage between an input shaft and an output shaft can be carried out while restraining an abrupt change in torque transmitted therebetween.
In a transmission comprising, an input shaft, an output shaft, and a first clutch including a first upstream rotary member rotationally connected to the input shaft to be driven by the input shaft, and a first downstream rotary member to be driven by the first upstream rotary member and rotationally connected to the output shaft to drive the output shaft and to be driven by the output shaft, wherein the first upstream and downstream rotary members are adapted to be selectively engaged with each other and disengaged from each other, the transmission further comprises, an output shaft driving device for applying a torque to the output shaft at least when the first upstream and downstream rotary members are disengaged from each other. The output shaft driving device may includes a second upstream rotary member to be driven by the input shaft and a second downstream rotary member to be driven by the second upstream rotary member to drive the output shaft so that the torque transmitted by the output shaft driving device from the second upstream rotary member to the second downstream rotary member is variably adjustable by changing a slipping or attracting degree (torque transmitting degree) between the second upstream and downstream rotary members when a rotational speed of the output shaft is smaller than that of the input shaft, or the output shaft driving device may be an electric motor for applying the torque to the output shaft.
By the output shaft driving device, an engage and/or disengage through the first clutch between the input shaft and the output shaft can be carried out while restraining an abrupt change in torque transmitted therebetween.
It is preferable for restraining the abrupt change in torque transmitted between the output and input shafts that the first upstream and downstream rotary members are disengaged from each other after the torque applied by the output shaft driving device to drive the output shaft is gradually increased, that the torque transmitted by the output shaft driving device to drive the output shaft is decreased after the first upstream and downstream rotary members are engaged with each other, that the torque applied by the output shaft driving device to the output shaft is adjusted in such a manner that a difference in rotational speed between the first upstream and downstream rotary members is kept within a predetermined range just before the first upstream and downstream rotary members are engaged with each other, and/or that the torque applied by the output shaft driving device to the output shaft is adjusted in such a manner that a difference in rotational speed between the first upstream and downstream rotary members just after the first upstream and downstream rotary members are disengaged from each other is kept within a predetermined range (a difference between the torque applied by the output shaft driving device just after the first upstream and downstream rotary members are disengaged from each other and the torque transmitted between the input shaft and the output shaft just before the first upstream and downstream rotary members are disengaged from each other is kept within a predetermined range).
When the transmission further comprises, a counter shaft through which the first clutch is rotationally connected to the output shaft to be driven by the input shaft so that the first upstream rotary member is driven by the input shaft, the first downstream rotary member is driven by the first upstream rotary member to drive the output shaft through the counter shaft, and the first downstream rotary member is driven by the output shaft through the counter shaft, a pair of first and second gears, the first gear being adapted to be driven by the counter shaft, the second gear being adapted to be driven by the first gear to drive the output shaft, and the first and second gears mating with each other, and a second clutch including a second shaft-side rotary member rotationally fixed to one of the counter shaft and the output shaft, and a second gear-side rotary member rotationally fixed to one of the first and second gears in such a manner that the input shaft is permitted to be rotationally connected to the output shaft through the second shaft-side and gear-side rotary members and the pair of first and second gears, so that the second shaft-side rotary member is adapted to be selectively engaged with the second gear-side rotary member and disengaged from the second gear-side rotary member,
it is preferable for restraining the abrupt change in torque transmitted between the output and input shafts that the torque applied by the output shaft driving device to the output shaft is adjusted in such a manner that a difference in rotational speed between the second shaft-side and gear-side rotary members obtainable when the first upstream and downstream rotary members are engaged with each other is kept within a predetermined range just before the second shaft-side and gear-side rotary members are engaged with each other, that the torque applied by the output shaft driving device to the output shaft is adjusted in such a manner that a difference in rotational speed between the second shaft-side and gear-side rotary members just after the second shaft-side and gear-side rotary members are disengaged from each other is kept within a predetermined range (a difference between the torque applied by the output shaft driving device just after the second shaft-side and gear-side rotary members are disengaged from each other and the torque transmitted between the input shaft and the output shaft just before the second shaft-side and gear-side rotary members are disengaged from each other is within a predetermined range is kept within a predetermined range), that the torque applied by the output shaft driving device to the output shaft is adjusted in such a manner that a difference in rotational speed between the first upstream and downstream rotary members obtained after the second shaft-side rotary member is engaged with the second gear-side rotary member is kept within a predetermined range just before the first upstream and downstream rotary members are engaged with each other, that the second shaft-side rotary member is disengaged from the second gear-side rotary member after the first upstream and downstream rotary members are disengaged from each other, that the torque applied by the output shaft driving device to the output shaft is gradually increased before the second shaft-side rotary member is disengaged from the second gear-side rotary member, and/or that the torque applied by the output shaft driving device to the output shaft is decreased after the first upstream and downstream rotary members are engaged with each other while the second shaft-side rotary member is kept engaged with the second gear-side rotary member.
When the transmission further comprises, another pair of first and second gears, the first gear being adapted to be driven by the counter shaft, the second gear being adapted to be driven by the first gear to drive the output shaft, the first and second gears mating with each other, and a reduction gear ratio of the pair of first and second gears being larger than that of the another pair of first and second gears, and a third clutch including a third shaft-side rotary member rotationally fixed to one of the counter shaft and the output shaft, and a third gear-side rotary member rotationally fixed to one of the first and second gears of the another pair so that the input shaft is rotationally connected to the output shaft through the third shaft-side and gear-side rotary members and the another pair of first and second gears, wherein the third shaft-side rotary member is adapted to be selectively engaged with the third gear-side rotary member and disengaged from the third gear-side rotary member, and the second clutch and third clutch are cooperative in such a manner that the third shaft-side rotary member is engaged with the third gear-side rotary member when the second shaft-side rotary member is disengaged from the second gear-side rotary member and the third shaft-side rotary member is disengaged from the third gear-side rotary member when the second shaft-side rotary member is engaged with the second gear-side rotary member,
it is preferable for restraining the abrupt change in torque transmitted between the output and input shafts that the torque applied by the output shaft driving device to the output shaft is gradually increased before the third shaft-side rotary member is engaged with the third gear-side rotary member after the second shaft-side rotary member is disengaged from the second gear-side rotary member, and/or that the torque applied by the output shaft driving device to the output shaft is adjusted in such a manner that a difference in rotational speed between the third shaft-side rotary member and the third gear-side rotary member obtainable when the first upstream and downstream rotary members are engaged with each other is kept within a predetermined range just before the third shaft-side rotary member is engaged with the third gear-side rotary member.
A peripheral total number of teeth of the first gear of the another pair may be smaller than that of the second gear of the another pair so that a rotational speed of the output shaft is lower than that of the input shaft.
When a peripheral total number of teeth of the first gear of the another pair is larger than that of the second gear of the another pair so that a rotational speed of the output shaft is higher than that of the input shaft, it is preferable for restraining the abrupt change in torque transmitted between the output and input shafts that the output shaft driving device includes a one-way clutch for transmitting the torque through the output shaft driving device when the rotational speed of the output shaft is lower than that of the input shaft and preventing the torque from being transmitted through the output shaft driving device when the rotational speed of the output shaft is higher than that of the input shaft.
It is preferable for speedy rotational speed control of the counter shaft that the first upstream and downstream rotary members are engaged temporarily with each other to decrease a difference in rotational speed between the first upstream and downstream rotary members while increasing the torque applied by the output shaft driving device to the output shaft, before the third shaft-side and gear-side rotary members are engaged with each other after the second shaft-side rotary member is disengaged from the second gear-side rotary member after the first upstream and downstream rotary members are disengaged from each other.
It is preferable that a radial inside of at least a part of the counter shaft while being prevented from including a gear train between the output shaft driving device and the output shaft.